In the craft industry different tools are known for cutting holes in walls and boards. A kind of tool which is commonly used is the so-called holesaw. A holesaw is a circular sawing device which is usually connected to a drilling machine in order to provide a shearing force. The holesaw is generally shaped like a cup. The open end of the cup is provided with saw teeth, and the closed end of the cup is provided with a shaft. The shaft is connected to a rotating tool, as for instance a drilling machine. A considerable drawback connected to the use of this kind of holesaw is that the diameter of the hole which is to be cut is predetermined by the diameter of the holesaw. Another drawback is that increased diameter of the hole saw requires an increased torque in order to get sufficient rotation speed and cutting force. This puts restrictions on how large holes may be cut using common drilling machines. Holes with a diameter over 25 cm are problematic to provide by means of a holesaw and a common drilling machine.
Patent publication EP1923156 discloses a holesaw according to prior art, comprising a holesaw mandrel, a center bit, and a cage for the center bit and the holesaw mandrel. The cage comprises a polygonal shaft which transfers a rotational force for instance from a drilling machine to the center bit and the holesaw mandrel. This kind of holesaw has the drawback that the diameter of the hole is determined by the diameter of the holesaw mandrel and that the required torque becomes disproportionately high at larger hole diameters.
Patent publication U.S. Pat. No. 3,276,326 discloses a device for cutting of circular holes comprising a center point, a distance bar and a cutter head provided with for example an end mill. A power source is connected to the cutter head in order to provide a rotation of the mill. The disadvantage of this device is that the electric tool is situated close to the cutter head, and thus hinders access in situations where the cutter head has to cut close to another object. Access is for instance hindered when cutting holes in a wall where the hole has to be cut close to the wall or close to a corner. Patent publications U.S. Pat. No. 3,146,675 and U.S. Pat. No. 3,124,182 also disclose similar solutions having the same drawbacks as described for U.S. Pat. No. 3,276,326.
Patent publication U.S. Pat. No. 4,397,593 discloses a device for cutting circular holes, comprising a center bit and a mill connected to a series of gear wheels which again is enclosed by a house. A drilling machine may be connected to the center bit and transfers a rotary motion to the mill through the series of gear wheels. The distance from the center bit to the mill may be regulated by adjusting the series of gear wheels such that holes of different diameter may be cut. This inventions shows advantages compared to other prior art by the feature that the drilling machine may be connected to the center bit and that the size of the hole may be changed. However, the disadvantage of this solution is that the geometry of the house hinders the access in situations where the hole has to be cut close to an obstruction. Furthermore, the device has a limitation with regards to the smallest and the largest hole diameter which may be cut. When cutting very different hole diameters, different variants of the tool may be used, where the different variants have shorter or longer series of gear wheels arranged in houses of different sizes.
Thus, there exists a need for a device for cutting of openings in plate-shaped bodies, wherein the device has the following properties:                the device allows making of holes with a diameter larger than 20 cm using the power which is available from a common drilling machine;        the diameter of the hole may be freely chosen; and        the shape of the device allows for cutting of holes close to walls and corners.        